Centrifugal spark control mechanism for flywheel magnetos



Nov. 13, 1945. R. E. PHELON 2,388,994

CENTRIFUGAL SPARK CONTROL MECHANISM FOR FLYWHEEL MAGNETOS Filed Aug. 11, 1944 2 Sheets-Sheet 1 f g 1m MM l2 INVENTOR JPUJRStlZ EPf/El o/v ATTORNEYS Nov. 13, 1945. R. E. PHELON 2,388,994

PARK CON R0 FOR FLYW EL MA NETOS Filed Aug. 11, 1944 2 S eeee s-Sheet 2 series of fan blades formed on said wall.

Patented Nov. 13, 1945 CENTRIFUGAL SPARK CONTROL MECHA- NISM FOR FLYWHEEL MAGNETOS Russell E. Phelon, West Springfield, Masa, assignor to Wico Electric Company, West Springfield, Mass., a corporation of Massachusetts Application August 11, 1M4, Serial No. 549,091

3 Claims.

This invention relates to an automatic spark advance mechanism for flywheel magnetos.

The problem of providing in a flywheel magneto for the automatic control of the spark in response to variations in engine speed, is difllcult because of the lack of space within the flywheel and, particularly is this so in the very small flywheels, which are now frequently used and are only a few inches in diameter. The small space within these small flywheels is so crowded with magneto parts that there is no room left for governor weights of any substantial size nor is there room for such weights to swing.

This invention has for an objectthe provision in a flywheel magneto of an automatic spark control mechanism, in which the governor weight or weights are located outside the flywheel, where they may be as large as is necessary to get effective action and where there is ample room for these weights to swing, and in which the part within the flywheel occupies so small a space as to be for all practical purposes negligible.

This invention will be disclosed with reference to the accompanying drawings, in which Fig. 1 is an end elevational view of a flywheel magneto embodying the invention;

Fig. 2 is a sectional view, looking in the same direction as Fig. land showing the magneto elements housed within the flywheel, the spark.

timing mechanism being shown in retarded position;

Fig. 3 is a sectional view taken on the line 33 of Fig.2; and

Fig. 4 is a fragmentary sectional view taken similarly to Fig. 2 but showing the spark timing mechanism in advanced position.

Referring to these drawings, the spark timing mechanism of this invention includes a governor weight I (Fig. 1) fixed to the outer end of a small shaft 2. which is rotatably mounted in the hub of a flywheel 3 (Fig. 3) and is located parallel with the axis of the flywheel. A spring 4 (Fig. 1) interconnects an outer corner of weight I to any suitable fixed point in the end wall of the flywheel and, as shown, to one of a The spring 4 tends to hold weight in the position illustrated by full lines in Fig. l in which position the weight abuts a limit stop 6 fixed in said wall of the flywheel.- Another and similarly fixed limit stop I is adapted, to be engaged by the weight I, when it is swung outwardly by centrifugal force, to limit the outwardmovement of the weight to the position shown by dotted lines in Fig. 1. The inner end of shaft 2 (Fig. 3) is formed with an integral crank 8, the crankpln portion of which is engaged in a longitudinallydirected slot 9 in the breaker-point cam of the magneto. As the governor weight 4 moves from the full line position to the dotted line position of Fig. 1, the breaker point cam is moved'from the full retard position shown in Fig. 2 to the full advance position shown in Fig.4.

The invention has been shown, by way of il-' lustrative example, in connection with a flywheel magneto of the type disclosed in the Harmon Patent No. 2,101,392, granmd December 7, 1937. This magneto will be briefly described herein, reference being had to said patent for a full disclosure if such is necessary or desired. In the following description, the reference numeralsindicate the same parts as in the patent.

The field structure is fastened in the rim portion id of the flywheel and consists of a perms-'- nent magnet Hand laminated pole shoes l2. The stator comprises a laminated structure having three legs l3, l4, and i5, integrally united at their inner ends and having their outer ends shaped to cooperate with the surfaces i6 of pole shoes l2 during rotation of the rotor. Primary and secondary coils iii and it are mounted on the leg H. The relatively fixed and movable breaker points are respectively shown at l9 and 20. The point i9 is fixed to and insulated from a bracket 2!. The point 20 is fixed to one end of a breaker lever 22, pivoted at 23 and having its other end riding on the periphery of a breaker cam 24. This cam, unlike the cam of the patent, is free to turn on the engine crankshaft 25, being relatively moved as and to the extent, above described. The flywheel l is fixed to the crankshaft 25. The breaker lever 22 has a spring 26 urging it towards cam 24 and the latter has a low surface 21 which allows the breakers l9 and 20 to close, the remainder of the cam being such as to hold the breaker points open. The condenser is shown at 28 and 29 is the electrical connection from the ungrounded terminal of the primary coil to the insulated terminals of the condenser 28 and to the insulated breaker point I9. 30 is the high tension wire leading from the ungrounded terminal of the secondary coil. The core structure is fixed by cap screws 3| to a stator plate 32, which in turn is fixed by screws 33 to a part 34 of the engine crankshaft.

The operation of the magneto is the same as that of the patent except that the governor arrangement, first above described, affords an automatic spark advance. The magneto is started with a retarded spark, as is desired for cranking, by means of the governor weight 8, which then occupies the full line position shown in Fig. 1. As the engine speeds up, centrifugal .counterbalancing is old and well understood in the art so that illustration of it here is thought unnecessary. V

The automatic spark control mechanism of this invention is characterized by its extreme simplicity. There are very few parts and each part is simple and capable of being easily and cheaply produced. The assembly of these few parts is also simple and capable of being performedquickly and easily. Before the flywheel is placed on the crankshaft, the shaft 2 is pushed into its hole in the hub of the flywheel, working from the inside of the flywheel. Then the weight 41 is pinned to the protruding end of the shaft 2 and this holds the shaft axially in position. The limit pins 5 and t are driven into the flywheel and spring i is applied to hold the weight in retarded position. The cam 2 is then turned on the crankshaft into retard position, after which the flywheel is thrust axially on the shaft with the crankpin of crank it entering groove 9. The flywheel is then put in place on the crft 25 and fastened as indicated to complete the assembly.

This spark control mechanism occupies so little space inside the flywheel as to be negligible for all practical purposes. Only the crank 8 extends into the space inside the flywheel and, even then, the crankpin is located in the slot 9 in the cam and therefore does not occupy any additional space. The crank arm is of very small volume and occupies very little space, merely a small corner near the inner end face of the flywheel hub. And only a small space is needed to enable this crankarm'to swing throughout the desired range. Then also, the small space needed would otherwise be unoccupied. The automatic spark advance can thus be applied to a standard flywheel magneto without requiring any change other than the slotting oi the breaker cam and the omission of the key or pin which formerly held this cam to the crankshaft.

7 holdingsaid weight in its innermost radial posiaseaoes I I claim: 1. The combination in a flywheel magneto with the flywheel and its crankshaft, of a breaker cam mounted to turn on said shaft, a small shaft rotatably mounted in the flywheel in parallel and closely adjacent relation with said craft, said second-named shaft having its inner end extending into the space within the flywheel and engaged with said cam to turn the letter on the crankshaft when the second-named shaft is turned and having its outer end extending outside the flywheel, a governor weight mounted outside the flywheel and connected to turn said seccud-named shaft back and forth when the weight swings outwardly and inwardly by centrifugal force, and yieldable means acting on said weight in opposition to centrifugal force.

2. The combination in a flywheel magneto with the flywheel and its crankshaft, of a breaker cam mounted to tum on said shaft, 9. email shaft rotatably mounted in the flywheel in parallel and closely adjacent relation with said crankshaft, said second-named shaft having its inner and extending into the space within the flywheel and having a crank, said cam having a slot in its periphery in which the crankpin of said crank is engaged, whereby to turn the cam on the crankshaft when the second-named shaft is turned,

said second-named shaft having its other end extending outside the flywheel, a governor weight mounted outside the flywheel and'connected to 'turn said second-named shaft back and forth when the weight swings outwardly and inwardly by centrifugal force, and yieldable means acting on said weight in opposition to centrifugal force.

3. The combination in a flywheel ma neto with the flywheel and its crankshaft, of a breaker cam mounted to turn on said shaft, a small shaft rotatably mounted in the flywheel in parallel and closely adjacent relation with said crankshaft.

said second-named shaft having its inner and ex"- tion and against one of said stops.

RUSSELL E. PHELON. 

